This application claims the priority benefit of Taiwan application serial no. 89110763, filed Jun. 1, 2000, the full disclosure of which is incorporated herein by reference.
1. Field of Invention
The present invention relates to an electrochemical electrode test strip and a process for preparation thereof. More particularly, the present invention relates to an electrochemical electrode test strip that utilizes a reactive film that contains an active species that can undergo redox reactions to contact with a sample, than a specific biochemical or chemical redox reaction occurs to transfer electrons between the active species and the an analyte of the sample. The electrochemical electrode test strip needs only low sample amount, and it is disposable.
2. Description of Related Art
Electrode test strips are not a new technology. In present market, electrode test strips are applied to produce various blood glucose test strips that can be used in home. But there still are some problems of the reactive region design for a test strip. Therefore, the sample adding method and the sample volume needed often introduce contamination and insufficient sample volume, and hence measurement errors are produced. For example, the time needed to introduce sample for fulfilling the reactive region is too long to give rise to reaction time delay. Or fingertips touch the reactive region to containment the test strip; therefore the test result errors are produced. Especially, when the lancet is used to gather blood from the babies and the olds, the blood volume is hard to reach the optimum volume, and test errors are occurred. Hence, a test strip that needs only minimal sample volume is required. Below 5 xcexcL sample volume is preferred for a siphonal test strip.
In FIG. 1, a perspective view of a commercialized blood-glucose electrode test strip is shown (U.S. Pat. No. 5,120,420). This test strip includes an insulating base plate 101, and a two-electrode system 102 is formed thereon. A second insulating layer 105 covers the insulating base plate 101, wherein an U-type opening 103 exposes one end of the two electrodes 102 surface and opening 104 exposes the other end of the two electrode 102 surface. Electrodes exposed by opening 103 serve as cathode lead and anode lead respectively. The opening 104 serves to define a reactive region over the electrodes 102. A reagent covers the reactive region. After the reagent is dried, the mesh 106 completely covers the reactive region. An adhesive tape 107 with a hole 110 attaches to the upper surface of the mesh 106 to fix mesh 106 and protect the reactive region. The hole 110 serves as a sample inlet. Two slits 108 and 109 that lay beside the mesh 105 are used to discharge gas.
However, this type of test strip can only reduce the sample volume requirement down to 9 xcexcL. Besides, the gas discharging effect of the two slits 108 and 109 is poor.
In FIG. 2, a perspective view of another commercialized blood-glucose electrode test strip is shown (U.S. Pat. No. 5,120,420). This test strip includes a base plate 201, and leads 202, a working electrode 204, a reference electrode 205, a spacer 206 and a cover 210 are formed thereon. The central part of the spacer 206 is cut off to form a U-shaped space 207, which forms a sample loading space i.e. a reactive region. The space 207 has a sample inlet 208 and a gas outlet 209.
The forming method of a reactive film (not shown in FIG. 2) of the blood-glucose electrode test strip includes steps as follows. Leads 202 are covered by a carboxymethyl cellulose (CMC) aqueous solution, then the CMC aqueous solution is dried to form a hydrophilic CMC layer. A glucose oxidase (GOD) solution is spread and dried to form a GOD layer thereon. A hydrophilic PVP polymer solution is spread and dried to form a PVP layer thereon. Finally, an electron medium suspension solution is spread and dried thereon to form an electron medium layer. The CMC layer, the GOD layer, the PVP layer and the electron medium layer compose the reactive film on the reactive region.
The reactive layer described above is composed of four layers (a CMC layer, a GOD layer, a PVP layer and an electron medium layer), and a drying step is performed after solution of each layer described above is formed. Hence the procedure of producing the reactive layer is very complicate. Besides, the time for a sample fulfill the space 207 to initiate the electrodes 204 and 205 working needs a certain period of time, which results in a measurement delay and thus measurement errors are produced.
The invention provides an electrochemical electrode test strip that has three sample inlets. A sample can be introduced from one of the three inlets, and the other two inlets can serve as gas outlets. The design of the electrochemical electrode test strip can provide a more convenient way to operate it.
The invention provides a different electrochemical electrode test strip, which has a sample inlet and two gas outlets. The time needed for the sample to fulfill the reactive space is shortened to reduce the detecting errors.
The invention provides an electrochemical electrode test strip that the sample volume needed is less than 5 xcexcL.
The invention provides an electrochemical electrode test strip that the sample volume needed is fixed to minimize the detecting errors caused by different sample volume.
The invention provides an easy method to produce an electrochemical electrode test strip. This method simplifies the producing process of a reactive film to shorten the time needed for mass-producing the electrochemical electrode test strip.
As embodied and broadly described herein, the invention provides an electrode test strip. The electrochemical electrode test strip comprises an insulating base plate, a electrode system on the base plate, a spacer which partially covers the electrode system and a channel trench with a constant width is formed thereof, a reactive film, and a cover on the spacer with an first opening thereof. Wherein the electrode system comprises at least a working electrode and a reference electrode, and the working electrode and the reference electrode is isolated. The reactive film contains at least one active species that can have a specific redox reaction with the analyte. The first opening exposes the channel trench, and two second openings are located at the two ends of the channel trench.
This invention also provides a method of manufacturing an electrode test strip, comprising the following steps. An insulating base plate is offered first. Than a layer of conductive films to be a cathode and an anode is printed on the insulating base plate, and the cathode and the anode are isolated. A first spacer and a second spacer on the conductive films is formed to expose two ends of the cathode and the anode, wherein a channel trench is formed between the first and the second spacer. A reagent solution is spread on a bottom surface of the channel trench, and then the reagent solution is dried to form a reactive film in the channel trench. The reagent solution contains an active species, a polymer, an electron medium, a nonionic surfactant and a buffer solution. A cover with a first opening is formed on the spacer, wherein the first opening is located on the channel trench and two second openings are surrounded by the insulating base plate, the first spacer, the second spacer and the cover.
According to the present invention, a sample can be loaded from one of the first and second openings into the reactive region of the electrochemical electrode test strip. Therefore, the sample can be easily loaded into the reactive region in a much shorter time and the sample can easily cover the reactive film completely, and thus larger redox current can be produced which can largely reduce the measure errors. Besides the reagent solution can be spread on the reactive region and dried in one time. This will safe much time and cost needed for manufacturing the electrode test strip.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.